Norm Walsh writes:
> NVDL is designed for namespace-based dispatching so it follows
> that it's a solution that can only be considered when different
> versions appear in different namespaces.
Yes, exactly, and there are many situations in which such
namespace-dispatching is natural and desirable. That said, I would prefer
that the TAG not appear to imply that such namespace-based composition of
vocabularies is the only one that's ever sensible. Note that I am >not<
suggesting that one avoid using namespaces; I think it's almost always
desirable to NS-qualify one's XML elements, and in some cases attributes
as well. I am saying that there are cases in which one wishes to
modularize markup in ways that are not best modeled as namespace-driven.
For example, one might in some organization use a handful of namespaces
for abstractions such as inventory, monetary abstractions, etc., and then
assemble schemas for particular document formats such as purchase orders
by quite freely mixing bits of markup from these namespaces. In such
cases, I think it's often more appropriate to suggest that the root
element name (not just its namespace) indicates the nature of the document
as a whole, with namespace-qualified markup mixed quite freely inside.
I'm not an NVDL expert, but my impression is that it's not focussed
primarily on such idioms. In summary, I have no problem pointing to NVDL
as an example of good practice for the things it does well; I would like
to avoid appearing in so doing to discourage use of languages in which
different versions share a namespace, or in which the same version of a
language freely mixes bits from many namespaces.
Noah
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Noah Mendelsohn
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
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